Looks like dry brush on cutouts were used to keep some form to the spinning, especially when the effect gets smaller. I absolutely love the instant no-nonsense cut to the tied up dog. No one frame to ease in to it, just spinning effects and he's there. It is giggle-worthy.

I think the best part of this scene is when each of the characters arrives at the window before walking the string. They stop themselves short and it's like their bodies stretch and wobble forward. Something like that. Anyway, to me it's more like feeling the movement than actually seeing it. I've always loved Clampett's cartoons, but looking at it from an analytical perspective lets you see how amazing it is. The guy's like a god.